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Re: [TowerTalk] Making an insulated base for 80 meter vertical from Rohn

Subject: Re: [TowerTalk] Making an insulated base for 80 meter vertical from Rohn 25
Date: Wed, 23 Dec 2009 12:15:14 -0500
List-post: <">>
One comment on Teflon.

It is SOFT and will deform rather easily under stress, whether  
expansion OR compression.  Do some testing before you put a lot of  
force on it.

My original idea was to use Teflon rod for my insulated tower bases,  
but changed that IMMEDIATELY upon discovering the deformation that  
occurred just with the weight of the base legs on the insulators in  
static position.

Now using (as previously done) fiberglass rod which can be purchased  
in 6' lengths at a farm supply store, disguised as 'electric fence  
posts'.  They are exactly the right size for my purpose, being 1.25"  
in diameter, and fit snugly within the tower leg supports.

Good luck,


> Hi Guys,
> I got a few emails asking where I got the insulated base. I made it. The
> insulated legs on the market are pretty expensive, and I didn't like that
> they  are in tension and compression when the tower moves with the wind and
> under  other external forces. It appeared to me, and I may be wrong, that the
> insulating material might not be as strong/durable as the original tower
> legs.
> I bought a  1" thick 24" square HDPE cutting board from a commercial
> restaurant supply , about 18 dollars, and drilled it to fit over the  
>   j-bolts in
> a standard Rohn 3'x3'x4' concrete tower base. I put the Rohn  tilt base on
> top of the cutting board. There are several machine shops on ebay  that sell
> PTFE teflon machining end pieces, leftovers. I bought a couple of  short 1
> 1/2" teflon rod pieces, 6 dollars, and drilled/turned them to fit  in the
> annular space between the bolt holes in the tilt base and the edges of  the
> j-bolts as insulating bolt sleeves. Then I took a short piece of 3" teflon
> rod, 3 dollars, and sawed 1/2" thick disks off of it. I drilled through the
> disks and made insulating washers for each of the base bolts.
> This way all of the plastic parts are always in compression, at their
> strongest. I used teflon for all of the parts that are exposed to the sun to
> avoid UV breakdown of the insulators, also teflon is a superior insulating
> material for the thinner (3/16" thick) bolt sleeves. By using the   
> tilt base, I
>  can lower the tower to make adjustments and repairs in the future ( not
> getting  any younger, hi hi).  I'm ready to install install the   
> tower sections
> and  run the feed line as soon as the weather clears up.
> Marty Haley AB5GU@ARRL.NET
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